Art of dewaxing hydrocarbon oils



March 26, 1935. R. H. GARDNER y1,995,740

y ART OF DEWAXING HYDROCARBON OILS Filed oct. 2o, 1931 fara /a fed Press/Poom Hes: /0

Pressed 0/7 /Veduc ing `W17/ ATTORNEYS Patented Mar.. .26, 1935 narranarverne f kwali@ garant @pp-ME,

Application otober 20, 1931i, erial No. 509,945

5 (Claims.

This invention relates to improvements in the production of neutral oilsand crystalline wax from paraiiin distillates. In referring to paramndistillates reference is intended to fractions inli cluding a majorportion of the crystalline wax In carrying out the present invention, achilled stock mixture including paraiiin distillate and a diluent oil oflower boiling range is pressed to separate crystalline wax from themixture, the diluent oil is distilled from the pressed stock mixture toseparate a neutral oil, or several neutral oils of varyingcharacteristics, therefrom, and a chilled stock mixture including theseparated wax and a diluent oil of boiling range lower than the wax andnot lower, advantageously higher, than the rst-mentioned diluent oil ispressed to separate crystalline wax from the mixture. Any includeddiluent oil may be distilled from the separated crystalline Wax.

The diluent oils which may be used with advantage in the iirst pressingoperation include naphtha, kerosene and gas oil. In referring tonaphtha, reference is intended to low boiling distillatev petroleumfractions such as, for example, distillate fractions having a boilingrange of 200-300 F. or 30D-400 F. The use of naphtha diluents affordssome advantages over the use of higher boiling kerosene and gas oildiluents in that equivalent viscosities can be obtained with lessdilution. In referring to gas oil reference is intended to distillatepetroleum fractions having a viscosity, for example, lower than about 50seconds (Saybolt-universal) and boiling generally upwards of 500 F. Theuse of gas oil diluents affords some advantages where extreme freedomfrom odor of the crystalline wax produced is important.

The diluent oils which may be used with ad-` vantage in the secondpressing operation include gas oiland pressed paraffin distillate. Theuse of a 'diluent on, particularly lower boiling aiment oils, in thefirst pressing operation apparently involves, at least in some cases,the separation of wax of unsatisfactory crystalline structure but, inthe combined operation of the invention, the use of a diluent oil,particularly a higher boiling diluent oil, in the second pressing operai tion apparently corrects this tendency.

(Cl. 19d-T19) Among the advantages oi the invention, the increase incapacity to be obtained with any given pressing plant is particularlyimportant. This increase in capacity appears in at least two aspects.First, the net capacity per press per day in terms of paraffindistillate pressed is substantially increased, in some cases as much astwo-fold or three-fold or more. Second, the invention makes it possibleto handle with economic advantage higher viscosity parafiin distillates,paraflin distillates having a viscosity of 150 seconds at 100 F. ascompared to parain distillates having a viscosity of 120 seconds at 100F. for example.

The following example of an operation embodying the invention, inconnection with which the accompanying drawing may be regarded as adiagrammatic ow sheet, will further illustrate the invention.

Parafiin distillate having a viscosity, for example, in the range of100-150 seconds at 100 F. is mixed in tank 1 with an amount of diluentoil suflicient to bring the viscosity of the mixture within the range,for example, of 50-80 seconds at 100 F., this mixture being effected ata temperature, for example, of 80-`100 F. A 48-50 API gravity, 3D0-400F. boiling range naphtha, or a 42-43 API gravity kerosene, or a 36-38API gravity -15" F. pour test gas oil, for example, is used as thediluent oil. The mixture from tank 1 is pumped through a series of heatexchangers 4, 5 and 6 and a pair of direct expansion ammonia chillers '7and 8 to an insulated storage tank 9. The mixture is cooled to atemperature, for example, of 50-70 F. as it leaves the heat exchanger 6and in the chillers 7 and 8 is brought to a temperature such that atemperature of 13 F. to +7 F. is maintained in the tank 9. From the tank9, the chilled mixture is pumped through a press 10, one of a seriesconnected by headers 11 and 12. This series of presses is arranged ininsulated rooms in which the temperature is maintained, for example, inthe range 5-30 F. The temperature of the pressed oil approximates, forexample, 530 F. As each press run is completed, the press is. unrackedand the separated slack wax, having a melting point of 92-105 F. forexample, is spudded from the press, melted, and discharged to a mixingtank 13. In the mixing tank 13 a diluent oil, 36-38 API gravity, 0-15 F.pour test gas oil for example, is mixed with the slack wax, atemperature of 1D0-115 F. for example being maintained in the mixingtank. This mixture is pumped through a series of heat exchangers 14, 15and 16 and a direct expansion ammonia chiller 1'1 to a press 18, one ofa series connected by headers 19 and 20. The mixture is cooled to atemperature, for example, of -90 F. as it leaves the heat exchanger 16and in the chiller 17 is brought to a temperature, for example,approximating 40-50 F. The pressed dlluent oil separated from thecrystalline wax in press 18 may be used as charging stock in a crackingoperation to produce gasoline. At the end of each press run, thecrystalline wax is spudded from the press, melted and discharged to'tank21 in which it is maintained at a temperature, for example, of 11S-120F. This wax may be discharged directly from the tank 21 to a sweatingoperation for the production of finished wax or it may be discharged toa reducing still 22 for the distillation from the wax oi any includeddiluent oil and from the reducing still discharged to a sweatingoperation for the production of iinished wax. The reducing still, forexample, may be a steam still or a iire and steam still. Any diluent oilseparated from the wax in the reducing still 22 may be utilized ascharging stock in a cracking operation for. the production of gasoline.repressed slack wax collected in the tank 21 may have a melting point,for example, of 115 F. and may comprise, for example, from 50-80% of thesingle pressed slack wax collected in the tank 13. The repressed slackwax discharged from the reducing still 22 may have a melting point, forexample, of 10T-120 F. The pressing operation carried out in the press10 may be carried out for the production, for example, of 0 F. pour testor 15 F. pour test neutral oils. Due to a limited solubility of wax inthe diluent oils, it is usually advantageous to carry out the iirstpressing operation at temperatures somewhat lower than that usuallyused. The pressed stock mixture separated in the press 18 is pumped inpart through the heat exchangers 6, 5 and 4 and in part through the heatexchangers 16, 15 and 14, being brought to a temperature, for example,of 80-90" F. by this heat exchange. The division of this stock betweenthe two series of heat exchangers may vary widely; three-fourths of itmay be passed through the heat exchangers 6, 5 and 4 and one-fourth ofit may be passed through the heat exchangers 16, 15 and 14 for example.Following this heat exchange, this pressed stock mixture is supplied toa reducing still (not shown) in which the diluent oil component of thestock mixture is separated from one or more neutral oils. Anyappropriate conventional reducing still may be used to carry out thispart of the operation; a pipe still-tower fractionating system forexample may be used with advantage.

I claim:

1. In the production of neutral oils and crystalline wax from paraiiindistillates, the improverI'hev ment which comprises pressing a chilledstock mixture including parafiin distillate and a diluent oil of lowerboiling range to separate wax from the mixture, distilling the diluentoil from the pressed stock mixture to separate a neutral oil therefrom,and pressing a chilled stock mixture including the separated wax and adiluent oil of boiling range lower than the wax and higher than thetiret-mentioned diluent oil to separate crystalline wax from themixture.

2. In the production of neutral oils and crystalline wax from parafiindistillates, the improvement which comprises pressing a chilled stockmixture including paramn distillate and a diluent oil of lower boilingrange to separate wax from the mixture, distilling the diluent oil fromthe pressed stock mixture to separate a neutral oil therefrom, pressinga chilled stock mixture including the separated wax and a diluent oil ofboiling range lower than the wax and higher than the iirst-mentioneddiluent oil to separate crystalline wax from the mixture, and distillingany included diluent oil from the separated crystalline wax.

3. In the production of neutral oils and crystalline wax from paraindistillates, the improvement which comprises pressing a chilled stockmixture including parafiin distillate and a kerosene diluent to separatewax from the mixture, distilling the kerene diluent from the pressedstock mixture to separate a neutral oil therefrom, and pressing achilled stock mixture including the separated wax and a gas oil diluentto separate crystalline wax from the mixture.

4. In the production of neutral oils and crystalline wax from paraiilndistillates, the improvement which comprises pressing a chilled stockmixture including paraiiin distillate and a naphtha diluent to separatewax from the mixture, distilling the naphtha diluent from the pressedstock mixture to separate a neutral oil therefrom, and pressing achilled stock mixture including the separated wax and a gas oil diluentto separate crystalline wax from the mixture.

5. In the production of neutral oils and crystalline wax from paraffindistillates, the improvement which comprises pressing a chilled stockmixture including paraiiin distillate and a diluent oil of lower boilingrange to separate wax from the mixture, distilling the diluent oil fromthe pressed stock mixture to separate a neutral oil therefrom, andpressing a chilled stock mixture including the separated wax and apressed paraiiin distillate diluent having a boiling range lower thanthe wax and higher than the firstmentioned diluent oil to separatecrystalline wax from the mixture.

ROBERT HENRY GARDNER.

